Corrosion of 304L stainless steel and chrome-plated drainage together with the ordinary black rubber and brass gaskets by stagnant solutions of sodium hypochlorite solutions

This paper presents the results of corrosion of 304L stainless steel sink, chrome-plated waste/drainage, brass and ordinary black rubber gaskets and putty by stagnant solutions of sodium hypochlorite. Three sets of experiments (Case A, Case B and Case C) were performed. In each experiment four 500 ml beakers were labeled solution 1, solution 2, solution 3 and solution 4. Each beaker contained a solution of sodium hypochlorite, a chrome-plated drainage (with ordinary black rubber and brass gaskets), and a sample of the 304L stainless steel cut from a 304L stainless steel domestic sink. For the cases (Case A and Case C) where the chemical resistance of the putty was tested another set of four beakers labeled solution 1, solution 2, solution 3 and solution 4 were used for the putty samples. Two sets of four concentrations were used. The concentrations considered were: Case A: 50 ml of sodium hypochlorite solution per litre of water, 40 ml of sodium hypochlorite per litre of water, 30 ml of sodium hypochlorite per litre of water and 20 ml of sodium hypochlorite per litre of water. The other set of concentrations used were: Case B and C: 50 ml of sodium hypochlorite per 5 l of water, 40 ml of sodium hypochlorite per 5 l of water, 30 ml of sodium hypochlorite per 5 l of water and 20 ml of sodium hypochlorite per 5 l of water. In the Case B experiments the solutions in the beakers were replaced with freshly prepared ones every two days during the observation of the samples. All the experiments were run at room temperature for 30 days. Case A: The results show that highly concentrated stagnant solutions of sodium hypochlorite corrode the chrome-plated waste/drainage, the brass gasket and dissolve the ordinary black rubber and the putty used to hold the chrome-plated waste/drainage in place. Case B: The formation of black/blue deposit was noted on the threaded part of all the chrome-plated waste/drainage in each of the four beakers. The amount of deposits formed increased with the duration of experiment. The changing of the solution every two days increased the amount of deposits formed. The ordinary black rubber gaskets were chemically resistant to all the solutions. Case C: Peeling off of chrome plating (from inside the chrome-plated waste/drainage) was observed in all of the beakers during the initial stage of the experiment and black deposits appeared on the top surface of the chrome-plated waste/drainage. The ordinary black rubber gaskets were chemically resistant to all the solutions. The putty samples became slightly blackish in all the four solutions. The 304L stainless steel sink sample did not corrode in all the solutions.